In a data communications system where a transmission resource is shared by multiple users, or where the transmission quality of a user can be affected by another user, there are generally two modes of channel operation. These may be referred to generally as an autonomous mode and as a scheduled mode. The autonomous mode does not necessarily require a resource request-grant relationship between the transmitters and the receiver prior to a communication, while the scheduled mode requires the presence of an arbiter of some type (e.g., at the receiver) to authorize and/or schedule transmissions for the multiple transmitters.
Each mode of operation has its advantages and its disadvantages. For example, the autonomous mode is well suited for small packet or circuit-like transmissions, while the scheduled mode is well suited for latency-insensitive transmissions.
For the cdma2000 1xEV-DV (or cdma2000, Revision D) reverse link framework, it is desirable to support both the autonomous mode and the scheduled mode of operation for the Reverse Supplemental Channel (R-SCH). However, many technical issues need to be resolved to make the autonomous and scheduled modes mutually compatible. For example, in order to operate these two modes alternatively, one important issue concerns how to best transition between the two modes.
Efforts have begun to standardize a complementary uplink structure, Enhanced Uplink Packet Access (EUPA) in 3GPP, to 1xEV-DV Revision D in 3GPP2. However, at present there is no provision for transitioning a mobile station between the autonomous and the scheduled transmission modes.
As a result, as presently specified the base station may not know, at any given time, when the mobile station needs to transmit data in the packet data system.